Axial piston variable displacement pumps with hydraulic swash plate actuators are disclosed in Malott U.S. Pat. No. 3,941,513 and in Marietta U.S. Pat. Nos. 3,945,764 and 4,162,874. In all of these patents, a horsepower control valve for the pump changes the torque limits of the pump in response to changes in the position of the swash plate actuator.